JEE Main 2025 Jan 22 Shift 1, Chemistry Q2: Atomic Structure

JEE Main2025Jan 22, Shift 1Chemistry

Which of the following statement is not true for radioactive decay ?

A
Amount of radioactive substance remained after three half lives is $\frac{1}{8}$ th of original amount.
B
Decay constant does not depend upon temperature.
C
Decay constant increases with increase in temperature.
D
Half life is $ln 2$ times of $\frac{1}{rate constant}$ .

Solution

The radioactive decay constant $λ$ is a nuclear property and is independent of external conditions such as temperature, pressure, or chemical state.

Hence the statement that the decay constant increases with temperature is false.

The other three statements are standard results: $N / N_{0} = (1/2)^{3} = 1/8$ after three half-lives, $λ$ is temperature-independent, and $t_{1/2} = \frac{ln 2}{λ}$ .

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